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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
July 14, 2010 - October 27, 2010
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
yes
Remarks:
no abiotic sterile control and no toxicity control
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Deviations:
yes
Remarks:
no abiotic sterile control and no toxicity control
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source: activated sludge from the aeration tank of the ARA Werdhölzi (CH-8048 Zürich), a municipal biological wastewater treatment plant (the sample was taken on July 12, 2010)
- Treatment: after sampling the sludge was aerated for 2 days. Prior to the test the sludge was washed twice with tap water and centrifugated.
- Concentration of sludge: 30 mg/L SS
Duration of test (contact time):
28 d
Initial conc.:
20 mg/L
Based on:
other: Total Organic Carbon (TOC in mg/L)
Initial conc.:
33.9 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: according to the OECD Guideline
- Additional substrate: not applicable
- Solubilising agent (type and concentration if used): not applicable
- Test temperature: 22 ± 2 degrees Celsius
- pH: at t=0 d: 7.4 ± 0.2; at t=28 d: 7.4 (test vessels); 7.5 (other vessels)
- pH adjusted: yes (if needed, at the beginning), to pH 7.4
- Aeration of dilution water: the test is aerated continously
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 2500 mL closed glass bottles, containing a total volume of 2000 mL test solution
- Number of culture flasks/concentration: 3 replicates, but for the evaluation of biodegradation, 2 of the 3 replicates were used
- Method used to create aerobic conditions: the test solution was aerated with CO2-free air
- Measuring equipment: the trapped CO2 was determined as inorganic carbon, which was determined with a Shimadzu TOC-5000A TOC-Analyzer (Shimadzu Schweiz GmbH, Römerstr. 3, CH-4153 Reinach, Switzerland) using the IC-mode. For each determination 3 single injections were performed.
- Details of trap for CO2: CO2 was trapped in gas-absorption bottles containing 125 mL of 0.13 M KOH

SAMPLING
- Sampling frequency: determinations were made on day: 1, 3, 7, 10, 14, 17, 21, 24 and 28

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3 replicates, but for the evaluation of biodegradation only 2 of the 3 replicates were selected and mentioned in the report (as a mean).
- Abiotic sterile control: not applicable
- Toxicity control: not applicable
Reference substance:
benzoic acid, sodium salt
Remarks:
(at 20 mg TOC/L)
Test performance:
The study was conducted according to OECD 301B and the validity criteria were fulfilled.
Key result
Parameter:
% degradation (CO2 evolution)
Value:
18.3
Sampling time:
3 d
Remarks on result:
other: Mean of 2 replicates
Key result
Parameter:
% degradation (CO2 evolution)
Value:
46.9
Sampling time:
7 d
Remarks on result:
other: Mean of 2 replicates
Key result
Parameter:
% degradation (CO2 evolution)
Value:
59.2
Sampling time:
10 d
Remarks on result:
other: Mean of 2 replicates
Key result
Parameter:
% degradation (CO2 evolution)
Value:
79.8
Sampling time:
14 d
Remarks on result:
other: Mean of 2 replicates
Key result
Parameter:
% degradation (CO2 evolution)
Value:
103.3
Sampling time:
28 d
Remarks on result:
other: Mean of 2 replicates
Details on results:
- See the section "Any other information on results incl. tables"
- In both replicates the degree of biodegradation reached >10% (the start of the 10-d window) at day 3
- In 1 replicate the pass level for ready biodegradability (>60%) was reached at day 10 (61.4%). In the other replicate it was just below 60% (56.9%).
- The next sampling time after this was day 14, which is 11 days after the start of the 10-d window. The degree of biodegradation in this other replicate was 77.8% at day 14.
Results with reference substance:
The reference substance reached 82% biodegradation after 14 days in 1 replicate (results other 2 replicates not reported)

Inoculum blank (mean of 2 replicates)

Replicate 1

Replicate 2

 

Replicate 3 (not used for evaluation)

Day

Total CO2 release (mg IC/L)

Total CO2 release (mg IC/L)

Degradation (%)

Total CO2 release (mg IC/L)

Degradation (%)

Mean degradation (%)

Total CO2 release (mg IC/L)

Degradation (%)

0

0.0

0.0

0.0

0.0

0.0

0.0

0

0,0

1

-0.2

0.2

1.8

0.2

1.7

1.8

-0,1

0,5

3

-0.1

3.3

16.9

3.8

19.7

18.3

2,5

13,0

7

0.6

10.0

47.2

9.9

46.7

46.9

8,6

40,0

10

1.1

13.4

61.4

12.5

56.9

59.2

12,4

56,5

14

1.5

17.8

81.9

17.0

77.8

79.8

17,3

79,0

17

1.4

19.1

88.8

18.5

85.4

87.1

19,4

90,0

21

1.3

20.7

97.1

19.8

92.4

94.8

21,5

101,0

24

1.3

21.5

101.3

20.5

96.1

98.7

22,8

107,5

28

1.2

22.3

105.6

21.5

100.9

103.3

24,1

114,5

Validity criteria fulfilled:
yes
Remarks:
; <20% difference between the replicates at the end of the test; the percentage degradation of the reference substance reached the pass level by day 14; the CO2 evolution in the inoculum blank at the end of the test did not exceed 40 mg/L (=10.9 mg IC/L)
Interpretation of results:
readily biodegradable
Conclusions:
Based on a study conducted according to OECD 301B and GLP with C-SAT 100090 (Dehyton ML), a degree of biodegradation of >60% was reached after 14 days. The validity criteria were fulfilled. The study only lacks the addition of a toxicity control. Based on the results of this study and the nature of the substance, the substance is considered to be readily biodegradable in accordance with the OECD Guideline.

Description of key information

Based on the results obtained with the key study, conducted according to OECD 301B and GLP, the substance is considered to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Screening for ready biodegradability

In a study conducted according to OECD 301B and GLP (reliability 1; key study) a degree of biodegradation of >60% was reached after 14 days. The validity criteria were fulfilled. Based on the results of this study and the nature of the substance, the substance is considered to be readily biodegradable in accordance with the OECD Guideline. In a study conducted according to OECD 301A and GLP (reliability 2), the threshold level of 70% of DOC removal was not obtained in 1 of the 2 replicates (the mean degradation after 28 days was 67%). The concentration of the inoculum was only 50 mL/L, while it may be up to 100 mL/L, which may explain the lower degradation. In addition, three studies have been performed similar to OECD 301E (reliability 4). The validity of these studies can not be assessed because only 1 replicate was used, no blank inoculum control was included and as the reports lack important details.

Screening for inherent biodegradability

From a study conducted similar to OECD 302B (reliability 4) and a study conducted similar to the draft OECD 302D guideline (reliability 4) it was shown that the substance is also inherently biodegradable under the conditions of the OECD Guideline. The validity of these studies cannot be assessed as no blank inoculum controls were included and as the reports lack important details.

This result is confirmed by a study published in the scientific literature (Garcia et al, 2008) in which a C12 imidazoline derivative was studied in accordance with ISO 14593 (reliability 4). The validity of this study cannot be assessed (and an IUCLID summary is not provided) as it is not determined whether the used test material is representative for the substance as defined in section 1 or not.

Screening for anaerobic biodegradability

That the substance is also biodegradable under anaerobic conditions was shown in a study published in the scientific literature (Garcia et al, 2008) in which a C12 imidazoline derivative was studied in accordance with the method described in Birch et al, 1989 (reliability 4). The validity of this study cannot be assessed (and an IUCLID summary is not provided) as it is not determined whether the used test material is representative for the substance as defined in section 1 or not.

 

References

Garcia, MT; Campos, E; Marsal, A; Ribosa, I. Fate and effects of amphoteric surfactants in the aquatic environment. Environment International 34 (2008), p. 1001-1005.

Birch, RR; Biver C; Campagna, R; Gledhill, WE; Pagga, U; Steber, J. Screening chemicals for anaerobic biodegradability. Chemosphere 19 (1989). P. 1527-1550.